Gutter Downspout Size Calculator

Doubling the number of downspouts halves the required capacity for each.

Gutter downspout size calculator. The size of the downspout should be constant through out its length. Now that we are well aware of the various gutter downspout sizes and styles let us dig deeper into the materials used for effective downspouts and how much they shall cost. Downspouts should be constructed with conductor. We recommend using this calculator as a basic tool to begin determining the requirements for your drainage system however all information should be verified by.

Start pressure length to the worst case and height difference. Northclad gutter size requirement calculator this calculator uses current data to calculate the required size of gutter as well as number and size of downspouts based on your input. Size downspouts to fit the gutter. For example a 6 inch k style gutter requires a 3 x 4 downspout while a 5 inch k style gutter uses a 2 x 3 downspout.

As far as downspouts go they run at 2 x3 and 3 x4 in size or 3 or 4 inches in diameter. First we will find the maximum amount of rain that will be captured in gallons per minute. 2 4 gutter and downspout sizing and location calculations both metric and english units. Now architects engineers designers and contractors can easily and accurately size downspouts and gutters according to the specifications in smacna s architectural sheet metal manual 7th edition 2012.

The downspout and gutter sizing calculator is located on the tools cad and apps page of the smacna website. This calculator serves as an information source only. Downspouts of less than 7 00 sq in 4515 sq mm cross section should not be used except for small areas such as porches and canopies. 3 more clicks will get a pump size if req d.

Gutter professionals have experience matching the gutters and the downspouts. We will use the larger of the two or 310 sq ft for our first calculation. Downspout sizes are based on table 1 3 dimensions of standard downspouts page 1 4 of the architectural sheet metal manual 7th edition. The second most common style of downspouts in urban homes is the rectangular downspout coming under a range of sizes such as 2 3 3 4 and 4 5.

A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. Downspout sizing in sizing downspouts the following considerations apply. Remember to save this spreadsheet to your own computer.

This calculator uses the equations that are laid out in the smacna handbook.